The following U.S. patents illustrate the best art known to the inventor at the time of the filing this application.
______________________________________ United States Letters Patent ______________________________________ 1,755,614 to Seil April 22, 1930 2,684,330 to French July 20, 1954 2,686,138 to Klein et al August 10, 1954 2,815,943 to Lamb December 10, 1957 2,826,209 to Klein et al March 11, 1958 3,150,007 to Kovachy September 22, 1964 3,880,965 to Dudis et al April 29, 1975 4,238,244 to Banks December 9, 1980 4,382,867 to Schmit et al May 10, 1983 4,419,141 to Kunkel December 6, 1983 ______________________________________